This weekend marks the birthday of perhaps the most-maligned president in American history. But was Andrew Johnson really that bad, or just the target of some second-guessing historians?

Johnson was born on December 29, 1808 in North Carolina. He served in the Senate and the House and as governor, and then military governor, of Tennessee. It was when he was serving as military governor that Abraham Lincoln asked him to replace Hannibal Hamlin as vice president in the 1864 campaign. A Democrat, Johnson switched parties for the election.

Already an enigma because of his well-known independent streak and his earlier support of slavery, Johnson turned heads when he was apparently drunk at his own inauguration in 1865. (Another theory was that Johnson was ill and he hadn’t been known for drinking in public.)

Johnson suddenly found himself as president when Lincoln died just after starting his second term. His policies during Reconstruction were controversial and caused his newfound party to impeach him in 1868. Johnson kept his job by one vote in a Senate trial.

“Although an honest and honorable man, Andrew Johnson was one of the most unfortunate of presidents. Arrayed against him were the Radical Republicans in Congress, brilliantly led and ruthless in their tactics. Johnson was no match for them,” says a bio prepared by Michael Beschloss and Hugh Sidey.

Looking back at historians who have ranked Johnson (and other presidents) since 1948, he appears to be the one president who has suffered at the hands of revisionist history—either because more facts are available about his term, or because his place in the history of race relations has been re-evaluated.

In 1948, historian Arthur M. Schlesinger, Jr. ranked Johnson as a middle-of-the-pack president: a respected 19th out of 29 presidents.

Since then, some presidents have risen in the eyes of historians, like James K. Polk and Andrew Jackson.

Andrew Johnson’s ratings have plummeted like a rock. In a recent 2010 Siena College survey, Johnson was called the worst president in history. A 2011 survey from a British academic institute ranked Johnson as 36th out of 40 presidents.

In general, two presidents who died early in their terms—William Henry Harrison and James Garfield—aren’t considered in presidential rankings.